| Anaphylactic
shock: an extreme bodily response
to an antigen, also sometimes referred to as
anaphylactic shock. Death can occur is breathing is constricted (from
swelling of the throat/airway and asthma) or blood pressure drops
(from fluid exiting the vascular system into hives/swelling). |
| Anaphylaxis:
an IgE-mediated response involving two or more
body systems (skin, airway, cardiac, gastrointestinal). Anaphylaxis
is caused by the body's release of mast cells, histamines, prostaglandins
and leukotrienes. While some symptoms of anaphylaxis can be helped
with antihistamines and vasodilation inhalers, the first line of treatment
should be epinephrine. |
| Antibody:
a substance created by the body when the immune system encounters
an antigen. Antibodies "mark" antigens
so the body can deal with them. Many antibodies can be measured with
RAST tests. |
| Antigen:
a scientific term for the food protein(s) to which a person is allergic.
It is also a general term to describe any substance that stimulates
the immune system. |
| Antihistamine:
a medication that helps the histamine portion
of an allergic response. Common brand names include Benedryl®
liquid, tablets and strips and Zyrtec® liquid. |
| EE:
eosinophilic esophagitis, an allergic condition affecting the esophagus.
Common in teen boys and men, this condition can cause heartburn, acid
reflux and difficulty swallowing. Food elimination diets can help
in some cases. |
Epinephrine
(norepinephrine) : a life-saving medication
that can reverse the effects of a severe allergic reaction by dilating
the airway and blood vessels (easing breathing and stopping the flow
of liquids out of the vascular system). Epinephrine is chemically
identical to adrenaline. The two terms may be used interchangeably.
Though British English usage may prefer 'adrenaline' over 'epinephrine,'
this difference appears to be fading from general use, perhaps because
of products like "Epi-pen."
Epinephrine is prescribed to food-allergic patients in the form of
a self-injection. Brand names include Epi-Pen® injectors and Twin-Ject®
injectors. |
| Norepinephrine,
while not chemically identical, may be preferred to epinephrine in
some hospital care scenarios. Norepinephrine is also an adrenergic
agonist which is used for its therapeutic benefits. It can be converted
into epinephrine enzymatically once administered.
Here's
a
link to chemical structures for all you chemists.
|
| Food
challenge: a controlled introduction of
a food to which an individual may be allergic used to verify the allergy
(or confirm if a child has outgrown an allergy). Food challenges are
usually done in the doctor's office or at the hospital. A gradually
larger dose of the food is given over fixed time intervals and the
patient observed for signs of a reaction. A blind food challenge
is where the patient does not actually know if the food being given
contains the allergen. |
| Histamine:
a chemical in the body that is released by the immune system in response
to an antigen. Histamines are the thing that
causes stuffy/runny nose, itching, hives and vomiting. An antihistamine
will alleviate these symptoms but will not prevent anaphylactic
shock. |
| IgE:
Immunoglobulin E, a substance the body creates in response to an antigen.
This substance can be measured in RAST tests.
When doctors refer to a food allergy, they are most typically talking
about this type of reaction. A common term in scientific literature
for this allergy is "IgE-mediated." |
| IgG:
Immunoglobulin G. Another substance that the body creates in response
to an antigen. IgG reactions are typically
gastrointestinal and cannot cause anaphylaxis. |
| Leukotrienes:
a substance created by the body that causes an inflammatory response
in response to an antigen. Because they can
cause long-term swelling and damage, many people with asthma take
a daily leukotriene-inhibiting medication such as Singulair® tablets. |
| Mast
cells: a special type of body cell involved in wound healing and
defence against pathogens. Mast cells can cause trouble when they
become sensitized to an antigen and settle in tissue. The most common
spots for them to settle are the skin, digestive tract and lungs.
When an allergen comes into the body, they release histamine.
|
| OAS:
Oral allergy syndrome. A pollen allergy that may cause food-allergic
symptoms in some individuals when foods are eaten that contain a similar
protein structure as the pollen. For example, an allergy to ragweed
pollen can cause some people to react to melons, banana and cucumber;
an allergy to birch pollen can cause some people to react to apples.
OAS symptoms are often seasonal when the offending pollen is present. |
| Prostaglandins:
a fat created by the body that influences mast cells and can contribute
to swelling and the allergic response. Prostaglandins are blocked
by steroids. |
| RAST:
radioallergosorbent test. A blood test
used to determine the different foods (antigens) a person may be allergic
to. RAST results are typically reported in units per liter (kU/l).
They are sometimes reported by "class", with levels ranging
from Class 0 (no antibody detected) to Class 6 (greater than 100kU/l
detected). |
| The
severity of a person's allergic response is not related to RAST level.
Class 3 individuals can have severe responses and Class 6 can have
mild. RAST tests are only useful to determine whether an individual
is allergy, not how allergic they are. However, different antigens
have different threshold levels above which an allergic response is
likely. For example, people with a peanut RAST result of >14kU/l
are likely to have an allergic response to peanut. Soybean typically
required >30kU/l; egg as little as 7kU/l. |
| Class
1 and Class 2 often fall below the threshold where most individuals
would experience a food reaction, so doctors often consider results
in this range equivocal. If results fall in this range and the patient
has not experienced an actual reaction to a food, the allergy may
be confirmed via a food challenge. |
| SPT
(or SP): Skin Prick Test. Used to diagnose
food allergies, most often in conjunction with patient history and/or
RAST testing. The allergist places a small amount
of the antigen being tested on the patient's
skin and scratches across it with a sterile needle. A skin wheel or
welt may signal an allergic response. While an anaphylactic reaction
is possible to an SPT, it is extremely rare (0.04% according to a
Mayo
Clinic source). SPT tests typically show about an 85% agreement
with RAST tests.* |
| Steroid
(corticosteroid): a medication (and natural body substance) used
to reduce swelling, especially long-term swelling that can persist
after an allergic reaction. |
| Wheal:
the swelling that occurs during a skin response to an antigen. The
size of the wheal is measured during a skin prick test.
A wheal of 5mm or greater is considered diagnostic of an allergy.
The size of the wheal does not correspond to the severity of allergic
response. |
